A shaped charge, in general, can have a metal charge case. High explosive material is disposed inside the case. A liner retains the explosive material in the case. A primer column can provide a detonating link between a detonating cord and the main explosive.
When the shaped charge is detonated a portion of the liner forms a jet portion which can be moving at a velocity of ˜1 km/sec. (tail) to ˜7 km/sec. (tip). The jet is propelled away from the case in a direction toward a target. Another portion of the liner is propelled away from the casing and forms what is known as a slug or carrot portion which is moving at a velocity of only a few hundred meters per second. When the shaped charge is used in a perforating gun, the target is normally the downhole formation rock. Upon detonation, the jet portion of the liner is propelled through the case and penetrates the downhole formation to enhance recovery of downhole hydrocarbons. The slug portion, in general, is designed to breakup to avoid plugging the hole on the casing formed by the jet.
Often times, about ˜30 percent of the shaped charge liner mass is converted into the jet. The jet density, velocity profile, jet material, jet straightness, and target properties determine the ability of the jet to penetrate a given target.
A factor determinative of the jet velocity profile is the thickness profile of the liner. More particularly, as described herein in connection with embodiments, a varying cross-sectional thickness of the liner can produce a jet formed of essentially separate parts (i.e., a segmented jet) that improves penetration over a single part jet (i.e., a linear jet). This idea is illustrated in FIGS. 7-9.
Liners for shaped charges can been fabricated using pure metals, alloys, ceramics or a combination of them. The metals used to form the liners can be powder metals, which may, for example, comprise of tungsten, lead or copper. Liners for shaped charges can be fabricated using different solid materials for the jet and the slug. One such example of a liner utilizes solid copper for the jet and solid zinc for the slug. Liners can be pressed, forged, or made by any other known production method.
Depth of penetration is important in the perforating art and constant improvement is desired. Embodiments herein address that issue and others related thereto.